The invention relates to a method for explosion protection of plants, pipelines and the like by monitoring chronologically successive values of the system pressure in potentially explosive areas and comparing these values with a predetermined pressure threshold, which is located above the system pressure prevailing at normal operating conditions by a certain safety margin; if this pressure threshold is exceeded certain explosion protection provisions, in particular isolating the explosion site behind a bulkhead and supplying extinguishing agents, are triggered. The invention also relates to an apparatus for performing this method.
In explosion protected plants it is known to monitor the course of pressure in the potentially explosive areas of the plant and if predetermined threshold values are exceeded to trigger explosion suppression by supplying extinguishing agents, flame arresters, bulkhead insulation and the like.
On the one hand, in principle, the goal of these explosion protection systems is to set the pres sure threshold that is effective for the triggering procedure only slightly above the normally prevailing system pressure, so that a potential explosion is recognized as soon as possible. On the other hand, however, the system pressure is subject to unavoidable fluctuations, whether from startup or shutdown procedures, from the opening of seals or valves, from changes in atmospheric pressure, or other causes. These harmless pressure fluctuations ought not to lead to triggering because each triggering results in interruptions in operation, and depending upon the kind of extinguishing agents used the plant must be thoroughly cleaned before it can be started up again.
Accordingly, the pressure threshold at which the explosion protection provisions are triggered has to be set a certain safety margin above the typically prevailing system pressure. Depending on the operating parameters, this safety margin is at least 100 to 200 mbar. This is true even if not only the static pressure level but also the speed of pressure change are monitored simultaneously.
As a result, the known plants can sufficiently reliably distinguish between dangerous and non-dangerous pressure increases. However, the fact that plant response is delayed by this safety margin means that in the case of danger a greater portion of the plant is affected by the explosion-caused pressure increase, and these parts of the plant must be able to bear a higher pressure load, and thus must be built correspondingly more sturdily and expensively as a result.